Mechanosensitive calcium flashes promote sustained RhoA activation during tight junction remodeling.

Area of Science:

• Cell Biology
• Epithelial Biology
• Mechanobiology

Background:

• Epithelial cell-cell junctions, specifically tight junctions (TJs), are crucial for maintaining barrier integrity.
• Mechanical stress can disrupt TJs, leading to leaks that require rapid repair mechanisms.
• The regulation of RhoA activation, known as 'Rho flares,' in TJ repair was previously unknown.

Purpose of the Study:

• To elucidate the regulatory mechanisms underlying Rho flares in epithelial tight junction repair.
• To investigate the role of intracellular calcium and mechanical forces in initiating the Rho flare pathway.

Main Methods:

• Utilized laser-induced and naturally occurring TJ disruptions in epithelial cells.
• Employed optogenetics to induce junction elongation.
• Manipulated intracellular calcium levels and inhibited mechanosensitive calcium channels (MSCs).
• Monitored calcium flashes and RhoA activation.

Main Results:

• Discovered that intracellular calcium flashes and junction elongation precede Rho flare activation.
• Demonstrated that TJ breaks trigger local calcium flashes.
• Showed that optogenetically induced junction elongation increases Rho flare frequency, indicating mechanical triggering.
• Found that calcium depletion or MSC inhibition reduces calcium flash amplitude and Rho flare duration.
• Established that MSC-dependent calcium influx is essential for maintaining barrier function through TJ protein reinforcement.

Conclusions:

• Identified a novel pathway where mechanosensitive calcium flashes initiate Rho flares for TJ repair.
• Highlighted the critical role of MSC-dependent calcium influx in epithelial barrier maintenance and TJ remodeling.
• Provided new insights into how epithelial cells respond mechanically to repair local leaks.